Characterization of tyrosine protein kinase associated with subcellular components of human colonic epithelium.
Tyrosine protein kinase (TPK) co-isolated with subcellular components derived from human colonic epithelium. The highest TPK activity, measured in the Triton X-100-insoluble cytoskeletal pellet, was directly related to the degree of malignancy of colonic tissue. TPK activity was assayed by measuring the incorporation of [gamma-32P] from [gamma-32]ATP into the synthetic polymer [Glu80Tyr20]n substrate. Lineweaver-Burk plots yielded an apparent Km of 167 micrograms/ml for [Glu80Tyr20]n and of 19 microM for ATP: Vmax for the phosphate donor was 0.9 nmol/min/mg protein. TPK activity was markedly stimulated by the metal ions Mg2+ and Mn2+ and significantly suppressed by tyrphostins, potent specific TPK inhibitors, shown to interfere with TPK-dependent growth processes. This is first report to present evidence for TPK activity associated with cytoskeleton-enriched subcellular preparations harvested from human colonic epithelium.
Schwartz
B
B
Gastroenterology Laboratory, Soroka Medical Center, Beer Sheva, Israel.
Cagnano
E
E
Braun
S
S
Lamprecht
S A
SA
D001597:Benzylidene Compounds / Q000494:pharmacology; D003106:Colon / Q000201:enzymology*; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000473:pathology / Q000648:ultrastructure; D003599:Cytoskeleton / Q000201:enzymology / Q000648:ultrastructure; D004848:Epithelium / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology* / Q000473:pathology / Q000648:ultrastructure; D007700:Kinetics; D008854:Microscopy, Electron; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*
D001597:Benzylidene Compounds; D011505:Protein-Tyrosine Kinases